Welding is a method of joining, or separating, metal objects. Arc welding is a common type of welding. An arc welding system typically is comprised of a power supply coupled by an electrical cable to a welding gun housing an electrode. A ground cable is used to connect the metal object to the power supply. When the electrode is placed against the metal object, the electrode in the welding handle completes an electrical circuit between the power supply and the metal object, allowing electrical current to flow through the electrode and metal object. The electrical current produces an arc between the electrode and the metal object. The heat of the electric arc melts the metal object in the region surrounding the electric arc. A filler material may be added to the molten metal. For example, a wire may be placed against the molten portion of the object, melting the wire and allowing the molten wire to merge with the molten object. Once the electrode is drawn away from the metal object, the circuit is broken and the molten mass begins to cool and solidify, forming a weld.
MIG (Metal Inert Gas) welding is one type of arc welding. MIG welding is also referred to as “wire-feed” or GMAW (Gas Metal Arc Welding). In MIG welding, a metal wire is used as the electrode. The wire is shielded by an inert gas and the metal wire acts as the filler for the weld. The inert gas is used to shield the molten metal from outside contaminants and gases that may react with the molten metal. Non-inert gases, such as CO2, may also be used in MIG welding.
The wire and gas are coupled through a cable to a welding gun. A typical welding gun used in MIG welding and similar welding systems has a handle and a neck that extends from the handle. The wire and gas are directed through the neck towards a workpiece. The neck typically has a nozzle assembly that is secured to the neck to direct the flow of wire and gas towards the workpiece. The wire is directed through a contact tip housed within the nozzle assembly. The electrical current is coupled from the cable to the wire through the contact tip. In addition, the end of the nozzle assembly typically has a cone-shape to taper the flow of gas from the welding gun. A typical welding gun has a switch, or trigger, that is coupled to the wire feeder. When the trigger is operated, wire is fed through the tip and gas is directed through the nozzle towards a workpiece.
Contact tips require frequent replacement during operation of the welding gun. Many contact tips are threaded into the welding gun. However, threadless contact tip designs also have been used. For example, threadless contact tip designs having a cam surface have been used. The cam surface is adapted to bind the contact tip against a stationary protrusion when the contact tip is rotated.
Unfortunately, there are a number of problems associated with existing threadless contact tip designs. For example, the process of binding the contact tip against the protrusion produces a bending stress in the contact tip. In addition, variations in the distance between the contact tip and the exterior portion of the nozzle, known as the tip-nozzle recess, occur with existing threadless contact tip designs. A consistent tip-recess distance is critical in certain welding applications, especially robotic welding systems. In addition, molten spatter from the weld may deposit on the end of the nozzle, eventually requiring replacement of the nozzle. Consequently, nozzles having a nozzle body and a removable threaded end section have been developed. However, weld spatter may contaminate the threads or the threads may experience galling, requiring a tool, such as a wrench, to remove the threaded end section from the nozzle body.
There exists then a need for a welding gun that utilizes a threadless contact tip design. Additionally, there is a need for a welding gun that enables a contact tip to be installed and removed without the use of tools. Furthermore, there exists then a need for a welding gun that utilizes a removable nozzle end piece that may be secured and removed without the use of tools. Finally, there exists a need for a nozzle assembly having a removable nozzle end piece and/or a threadless contact tip that produces a consistent tip-recess distance.